[Objective] The aim was to provide the technical reference for scientific storage of walnuts.[Method] Using walnuts produced in Cheng country in Gansu province as tested material,the unshelled walnuts were cased in 30 μm purple PVC bags,30 μm white PVC bags and general 40 μm polyethylene plastic bags,resp.for spontaneous storage at modified atmosphere and the fatty acid oxidation changes of walnuts for 180 d storage at room temperature were studied.[Result] When walnut storage was for 30 d,the O2 content in PVC bags was lowest and the CO2 content was highest.During storage,the total fat content,iodine value all declined,and the peroxide value and saponification value all rose.The 30 μm purple PVC bags were effective to inhibit degradation of the total fat.The acid value,peroxide value and saponification value of walnuts cased in 30 μm purple PVC bags were lower than that cased in 30 μm white PVC bags and 40 μm polyethylene plastic bags,but the iodine value was opposite.[Conclusion] MAP could inhibit the fatty acid oxidation of walnuts better and was preferable to maintain the quality of walnuts.The effect of storing walnuts cased in 30 μm purple was the best.